Exhaust gas recirculation valve

ABSTRACT

A dual diaphragm operated control valve assembly, responsive both to a pressure signal created at an induction passage slot traversed by the edge of the throttle and to manifold pressure, controls recirculation of exhaust gases from the intake manifold exhaust crossover passage to the intake manifold induction passages.

United States-Pat ent 1 9i Thompson Apr. 2, 1974 [54] EXHAUST GASRECIRCULATION VALVE 2,722,927 11/1955 Cornelius 123/119 A 3,713,428 7H1973 Sandhagen.... l23/ll9A [751 Invent 3P?" Thompson Grand Blanc3,717,131 2/1973 Chana c 111 1231119 A 1c Assigneei Mfnors 'l PrimaryExaminerWendell E. Burns Detro1t, Mich. Attorney, Agent, or FirmC. K.veenstra [22] Filed: Nov. 17, 1972 21 Appl. 190.: 307,439 1 ABSTRACT Adual diaphragm operated control valve assembly, 52 us. c1 123/119 Arespmlsive b a Pressure Signal mated at 51 1111.01 F02m 25/06ducmn'passage '"aversed bYlhe edge 0f the [58] Field of Search 123/119 Athmme e i f Pressure 60mm recircula' tion of exhaust gases from theintake manifold exhaust [56] References Cit-ed crossover passage totheintake manifold induction UNITED STATES PATENTS l/l961 Skiruin et'al.12 3 119 A passages. 1

' 1 Claim, 2 Drawing Figures EXHAUST GAS RECIRCULATION VALVE in thecombustion chamber, dilute the air-fuel mixture 8 to inhibit formationand emission of oxides of nitrogen.

In that system, the vacuum signal is increased as the throttle traversesthe slot, and the valve is opened to permit increased recirculation ofexhaust gases. At the same time, however, the manifold pressure isincreased which tends to reduce the recirculation of exhaust gases intothe induction system. In addition, the portion of exhaust gases tendingto remain in the combustion chamber reduces as the manifold pressureincreases. Thus to provide the desired proportion of exhaust gases inthe combustion chamber, it may be necessary to increase the portion ofexhaust gases which are recirculated as the manifold pressure increases.Therefore, while the aforementioned control valve assembly may beproperly calibrated to achieve a certain inhibition of the formation andemission of oxides of nitrogen, the achievement of greater inhibitionmay not be practical with that structure alone.

This invention provides an improved valve assembly containing means forincreasing exhaust gas recirculation as manifold pressure increases. Theimproved as- I sembly includes two diaphragmsof differing effectiveareas defining a manifold pressure chamber therebetween. Upon anincrease in manifold pressure, the valve opening force is increased by aforce proportional to the increase in manifold pressure. The greaterflow area through the valve thereby provided compensates for the reducedpressure differential in the recirculation passage and thereducedresidual fraction in the combustion chamber to provide the desireddilution of the air-fuel mixture.

The details as well as other objects and advantages of this inventionare set forth in the remainder of the specification and are shown in thedrawing, in which:

F l6. 1 is a top plan view of a V-8 engine intake manifold containinginduction passages and an exhaust crossover passage, together with acarburetor spacer plate containing an exhaust gas recirculation passageand carrying an exhaust gas recirculation control valve assembly; and

FIG. 2 is a schematic sectional view of the FIG. 1 manifold and spacerplate showing the induction passage plenums and the exhaust crossoverpassage in the manifold and the exhaust gas recirculation passage in thespacer plate together with a carburetor throttle body, and in enlargeddetail, the dual diaphragm vacuum operated exhaust gas recirculationcontrol valve assembly.

Referring to the drawing, an intake manifold 10 has a pair of verticalprimary riser bores 12 and 14 and a pair of vertical secondary riserbores 16 and 18. Riser bores 12 and 16 open to an upper horizontalplenum 20 connected forwardly (leftwardly as viewed in FIG. 1) to a pairof transverse runners 22 and 24 and connected rearwardly (rightwardly asviewed in FIG. 1) to another pair of transverse runners 26 and 28.Similarly, riser bores 14 and 18 open to a lower horizontal plenum 30connected forwardly to a pair of transverse runners 32 and 34 andrearwardly to another pair of transverse runners 36 and 38.

An exhaust crossover passage 40 extends transversely from the left-handside of manifold 10 beneath plenums 20 and 30 and receives a portion ofthe exhaust gases discharged from the engine combustion chamber.

An insert plate 42 is secured on manifold 10 and has primary riser bores44 and 46 and secondary riser bores 48 and 50 which meet, respectively,riser bores 12, 14, 16, 18 of manifold 10.

A carburetor 52 is secured on insert plate 42 and has primary throttlebores 54 and 56 which meet, respectively, primary riser bores 44 and 46of insert plate 42. Carburetor 52 also has secondary throttle bores (notshown) which meet secondary riser bores 48 and 50 of insert plate 42.

A bore 58 in manifold 10 leads upwardly from exhaust crossover passage40 to the first portion 60 of an exhaust recirculation passage formed ininsert plate 42. The first portion 60 of the exhaust recirculationpassage leads through a control valve assembly 62 to a second portion 64of the exhaust recirculation passage. This second portion 64 dividesinto a pair of branches 66 and 68 which lead to the primary riser bores44 and 46 in insert plate 42.

It should be appreciated that both portions 60 and 64 of the exhaustrecirculation passage may be integrated in manifold 10 rather than inseparate insert plate 42.

Control valve assembly 62 is shown in detail in FIG. 2. It comprises abase member 70 having an upper wall 72, a peripheral wall 74, and alower wall 76 which define a chamber 78. Chamber 78 has an inlet 80opening from the first portion 60 of the exhaust gas recirculationpassage and an outlet 82 opening to the second portion 64 of the exhaustgas recirculation passage. A valve seat member 84 is threadedly securedin inlet 80 in a tamperproof location.

A valve pintle 86 has a generally conical contour cooperating with valveseat 84 to provide a variable area for flow of recirculated exhaustgases. Valve pintle 86 is retained on a valve stem 88 by staking the end90 of stem 88.

Stem 88 extends out of chamber 78 to a pair of diaphragms 92 and 94separated by a cylindrical spacer 96 surrounding stem 88. Stem 88 isupset at a point 98 just below diaphragm 94, and the upper end 100 isriveted over diaphragm 92. With this construction, diaphragms 92 and 94simultaneously control the position of pintle 86.

The details of construction of valve assembly 62 which support and guidethe central portion of valve stem 88, which seal around valve stem 88,and which minimize heat conduction from valve body 70 to diaphragms 92and 94 are set forth in Ser. No. 220,036, filed Jan. 24, 1972, and itsdisclosure is incorporated herein by reference.

I The lower side of diaphragm 94 is exposed to atmospheric pressure. Thechamber 102 formed between diaphragms 92 and 94 and enclosed by aplastic spacer 103 is subjected through a hose 104 to the manifoldprssure in the induction passages downstream of the carburetor throttles106 and 108. The chamber 110 formed above diaphragm 92 by a cover 111 issubjected through a hose 1 12 to the pressure signal created at a slotor port 1 14 opening from throttle bore 56. Slot 114 is disposedadjacent and extends above and slightly below the upstream edge 116 ofthrottle 108.

In operation, an air-fuel mixture, or air alone in the case of a fuelinjected engine, is drawn into the engine through the induction passagedefined by carburetor throttle bores 54 and 56, insert plate riser bores44, 46, 48, 50 and manifold riser bores 12, 14, 16 and 18, manifoldplenums 20 and 30, and manifold runners 22, 24, 26, 28, 32, 34, 36, 38.When throttles 106 and 108 are closed as shown in FIG. 2, thesubstantially atmospheric pressure in throttle bore 56 aove throttle 108bleeds into the upper portion of slot 114 and increases the manifoldpressure sensed by the lower portion of slot 114. The resultant pressuresignal delivered through hose 112 to chamber 110 is partially offset bythe lower pressure delivered through hose 104 to chamber 102.Simultaneously the atmospheric pressure below diaphragm 94 is partiallyoffset by the lower pressure in chamber 102. The combination of forceswhich is thus created on diaphragms 92 and 94 is insufficient to raisediaphragms 92 and 94 against the bias of a spring 120. Valve pintle 86is thereby maintained in engagement with valve seat 84 to preventrecirculation of exhaust gases through control valve chamber 78.

As throttles 106 and 108 are opened to a part throttle position, theupstream edge 116 of throttle 108 traverses slot 1 l4 and a greaterportion of slot 114 is subjected to the manifold pressure below throttle108 while a lesser portion of slot 1 14 is subjected to thesubstantially atmospheric pressure above throttle 108. This results in alower pressure signal which is transferred through hose 112 to chamber110. Simultaneously, a higher manifold pressure is transferred throughhose 104 to chamber 102. The combination of forces which is thus createdon diaphragms 92 and 94 raises diaphragms 92 and 94 against the bias ofspring 120. Valve pintle 86 is then lifted away from valve seat 84 torecirculate exhaust gases from exhaust cross-over pasage 40 through bore58, passage 60: inlet 80, chamber 78, outlet 82, passage 64, andbranches 66 and 68 to riser bores 44 and 46.

It will be appreciated that if diaphragms 92 and 94 had the sameeffective area, variation of manifold pressure in chamber 102 would haveno effect on operation of valve assembly 62. Valve assembly 62 thenwould be responsive solely to variation in the pressure signal createdat slot 114 in the manner set forth in US. Pat. No. 3,641,989.

It is noted that as throttles 106 and 108 are opened, the pressuresignal created at slot 114 is reduced but the manifold pressure and thusthe pressure in recirculation passage 64 is increased. Thus while pintle86 is displaced from valve seat 84 to increase recirculation of exhaustgases, the difference between exhaust gas pressure in passage 60 andinduction passage pressure in passage 64 is reduced. Further, theincrease in manifold pressure generally results in a reduction in theproportion of exhaust gases remaining in the combustion chamber. Thus toreach the desired inhibition of the formation and emission of oxides ofnitrogen, it may be necessary to supplement the pressure signal createdat slot 114 (which is designed to be proportional to the rate of airflow) with a signal indicating an increase in manifold pressure.

It is for this purpose that diaphragm 94 and manifold pressure chamber102 have been added to the previously known structure. Diaphragm 94 hasan effective area less than the effective area of diaphragm 92. As aconsequence, the upward force on valve stem 88 is created not only bythe constant atmospheric pressure against the bottom of diaphragm 94 butalso by the variable manifold pressure acting against the greater areaof diaphragm 92. Upon opening of throttles 106 and 108, the manifoldpressure increases and thus increases the upward or valve opening forceon stem 88. This adds to the displacement of pintle 86 from valve seat84 resulting from the reduction in the pressure signal acting againstthe top of diaphragm 92 and thereby provides increased area throughvalve seat 84 for recirculation of exhaust gases.

It should be pointed out that valve assembly 62 also is effective toprevent recirculation of exhaust gases during wide open throttleoperation. At such time, the pressure signal from port 114 is equal ornearly equal to the manifold pressure, and both approach atmosphericpressure. Thus the combination of forces on diaphragms 92 and 94 isinsufficient to overcome the bias of spring 120, and pintle 86 is biasedinto engagement with valve seat 84.

It will be appreciated, of course, that the size and shape of pintle 86,the size of diaphragms 92 and 94, the characteristics of spring 120, andthe shape and location of slot 114 all must be considered to achieverecirculation of exhaust gases in desired proportions to induction airflow and manifold pressure. The provision of a second diaphragm andpressure chamber permits an additional degree of control over exhaustgas recirculation.

It also will be appreciated that provision of means for increasingrecirculation of exhaust gases with increases in manifold pressure maybe desirable in other exhaust gas recirculation systems. For example, ina system which recirculates exhaust gases into a constant pressure zone,variations in manifold pressure would not affect the rate at whichexhaust gases are recirculated but would still affect the residualfraction of exhaust gases in the combustion chamber. Provision of meansto increase recirculation of exhaust gases with increases in manifoldpressure would compensate for the reduced residual fraction to providethe desired proportion of exhaust gases in the combustion chamber.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An exhaust gas recirculation control valve assembly for use on aninternal combustion engine having an induction passage for air flow tothe engine, a throttle disposed in said induction passage and rotatablebetween closed and open positions for controlling air flow therethrough,an exhaust passage for exhaust gas flow from the engine, a recirculationpassage having a first portion extending from said exhaust passage and asecond portion extending to said induction passage downstream of saidthrottle, said valve assembly comprising a base member having upper,peripheral, and lower walls defining a chamber, said lower wall furtherdefining an inlet for receiving exhaust gases from said firstrecirculation passage portion and an outlet for discharging exhaust gasto said second recirculation passage portion, a valve seat formed insaid inlet, a valve pintle associated with said valve seat forcontrolling exhaust gas flow therethrough, a valve stem secured to saidvalve pintle and extending through said chamber and said upper wall, afirst diaphragm secured to said valve stem outside said chamber, thelower side of said diaphragm being exposed to atmospheric pressure, asecond diaphragm secured to said valve stem above said first diaphragmand defining a second chamber between said diaphragms, means subjectingsaid second chamber to the pressure in said induction passage downstreamof said throttle, said-second diaphragm having an effective area greaterthan the effective area of said first diaphragm whereby the pressure insaid second chamber creates a greater force on the lower side of saidsecond diaphragm than on the upper side of said first diaphragm, meansdefining a third chamber on the upper side of said second diaphragm, andmeans subjecting said third chamber to the pressure signal created at aport in said induction passage disposed adjacent and traversed by theedge of said throttle.

1. An exhaust gas recirculation control valve assembly for use on aninternal combustion engine having an induction passage for air flow tothe engine, a throttle disposed in said induction passage and rotatablebetween closed and open positions for controlling air flow therethrough,an exhaust passage for exhaust gas flow from the engine, a recirculationpassage having a first portion extending from said exhaust passage and asecond portion extending to said induction passage downstream of saidthrottle, said valve assembly comprising a base member having upper,peripheral, and lower walls defining a chamber, said lower wall furtherdefining an inlet for receiving exhaust gases from said firstrecirculation passage portion and an outlet for discharging exhaust gasto said second recirculation passage portion, a valve seat formed insaid inlet, a valve pintle associated with said valve seat forcontrolling exhaust gas flow therethrough, a valve stem secured to saidvalve pintle and extending through said chamber and said upper wall, afirst diaphragm secured to said valve stem outside said chamber, thelower side of said diaphragm being exposed to atmospheric pressure, asecond diaphragm secured to said valve stem above said first diaphragmand defining a second chamber between said diaphragms, means subjectingsaid second chamber to the pressure in said induction passage downstreamof said throttle, said second diaphragm having an effective area greaterthan the effective area of said first diaphragm whereby the pressure insaid second chamber creates a greater force on the lower side of saidsecond diaphragm than on the upper side of said first diaphragm, meansdefining a third chamber on the upper side of said second diaphragm, andmeans subjecting said third chamber to the pressure signal created at aport in said induction passage disposed adjacent and traversed by theedge of said throttle.